1. Field of the Invention
This invention relates to a system for automatically acquiring non-program information for storage and display by a televisions receiver. More particularly, the present invention relates to a system for automatic switching between alternative signal inputs and the acquisition of a reliable signal source so that the non-program information is always available to the user of the television receiver.
2. Discussion of Related Art
A broadcast television signal is capable of carrying information which is not directly related to the television program meant to be seen by the television viewer. Such information might be program schedule information as provided by a system such as "INSIGHT" (Trademark), a product INSIGHT TELECAST, INC., Fremont, Calif. The INSIGHT system is the subject of U.S. Pat. Nos. 4,706,122 and 4,977,445 to Young. Reference may be had to these patents for further exposition of that subject matter.
Briefly, the INSIGHT system allows user selection of programs from schedule information transmitted to, stored in, and selectively displayed by the television receiver. The INSIGHT system, or other such program schedule information services, may provide updated program schedule information for several future days by broadcasting the program schedules in digital code, whence it is stored in the television receiving set for selective display and control of television programming by the viewer. It will be understood that other information may be similarly broadcast and utilized. This information, or data, will be generically referred to as non-program information.
The non-program information is envisioned to be broadcast by placing the information in the vertical blanking interval (VBI) of a wireless broadcast channel signal. This mode of delivery for the non-program information is envisioned because, barring extensive additional circuitry to the common television receiver and/or development of alternative broadcast media for the nonprogram information, this is the surest way to implement such a system.
But, problems arise when one takes into account that approximately 60% of all American homes rely on cable or wired signal transmission as their principle source for receiving television signals. A cable television company retransmitting the wireless broadcast may be reluctant to pass through non-program information transmitted in the VBI, in which case the television set of the cable viewer will not receive the nonprogram information transmitted in the wireless broadcast.
Another problem is that while a cable company may leave the non-program information signal in its retransmission, the cable decoder box used by cable television viewers who do not have "cable ready" sets, or who need the box to decrypt encrypted programs, transmits a signal only on channel 3 or 4 from the decoder box into the television set. Thus, the tuner on these viewers' sets will always be on channel 3 or 4. But, if the non-program information is broadcast on, e.g.. channel 11, the set will not be able to capture the non-program information, and it will be unavailable to the viewer.
Thus, a system is needed for automatically switching between a problematic cable signal and an alternative signal source which reliably provides the non-program information. It is an object of the present invention to provide a system for accomplishing this.